Scientists haven't yet discovered how many children, upon hearing of time travel, dream of heading back a few decades to visit their parents as kids. Stripped of height and authority, would parents be any fun? Maybe they would just be bossy, brutish, and short. Would they know how to play tag?

Exercise physiologists at the University of South Australia who analyzed research on 25 million children around the world determined that today's kids, on average, take a minute and a half longer to run a mile than did kids in 1975. The studies measured how far children of different ages could run in 5 to 15 minutes, and how quickly they could run distances up to two miles.

But do fleet feet really matter now that most of our predators, as well as our prey, are stored behind bars? Isn't texting speed more relevant to modern survival?

Apparently running still matters. According to these researchers and many others, several factors make running fitness a key measure of heart health.

The Associated Press reported details on the findings, which were fairly constant across gender and age groups: